(a) Field of the Invention
The present invention relates to a method of working and finish treating the surface of stones, preferably granite, for roughing the surface and for removing the gangue formed thereon in prior cutting and treatment steps.
(b) Related Art
A large quantity of various stones have been recently used to provide high grade buildings and to give depth impression. Demands for granite and marble are particularly high.
However, methods of working the stone surface are conventional. They are described in a literature "Think scientifically of stone working" published by Sekibunsha, pages 42 to 55.
Three conventional stone working methods 1 to 3 will be briefly described with reference to FIG. 22. Each of the methods 1 to 3 comprises the steps as follows.
1. Rubble, hump removing, chiseling finishing, bush hammering, (flame finishing), dabbed finished, grinding, honing and polishing
2. Rubble, cutting by a gang saw, bush hammering, (flame finishing), dabbed finishing, grinding, honing and polishing
3. Rubble, cutting by a circular saw cutting machine, honing, polishing, or bush hammering, (flame finishing), dabbed finishing, polishing
In this case, the flame finishing may be omitted The bush hammering may be omitted and the dabbed hammering may be directly performed.
The stones which have been subjected to the process proceeded to the step of polishing are mainly used as outer wall material requiring gloss. If gloss is not required, the stones subjected to the process which is terminated, for example, in step of bush or dabbed hammering before the step of polishing are practically used.
Particularly, if the stones are used as stepping-stones, the stones which have not reached the step of polishing are directly used for preventing pedestrian from slipping.
Since the process 1 requires a number of steps and high labor cost, the process 2 or 3 are most adopted.
Observation of such mechanically cut surface shows that the crystal particle groups p, p, . . . are flat on the surface as shown in FIG. 1 since they are sliced. Observation in more detail shows that small concaves and convexes and cracks are often formed as shown in FIG. 2 due to application of an external force. Many scratch stripes are formed by slicing. Accordingly, the cut stone looks very whitish on the surface thereof unlike untreated natural stone. Therefore, a working process proceeded to the polishing step after the above mentioned bush hammering or the dabbed hammering on one side of a stone panel is essential since the just cut stone has little commercial value. However, this polishing step requires much labor, resulting in a high manufacturing cost. The other side is unworked since it is not related with the appearance.
Although the above mentioned flame finishing may be performed to provide the mechanically cut surface with concaves and convexes, the problem of the whitish looking surface can be overcome to same extent. However, slightly whitish looking surface remains and the condition of natural stone can not be reproduced. The stone is heated to a high temperature by the flame finishing so that the thermal stress is very high. Therefore, the panel which is subjected to flame finishing should be 8 mm or more, at least 5 mm in thickness in order to prevent damages due to the thermal stress. Accordingly, the amount of stone per application area will be inevitably increased.